Exertional syncope: what to know

Syncope is a brief loss of consciousness caused by reduced blood flow to the brain, followed by recovery. During exertion, possible contributors include an abnormal heart rhythm, structural heart disease, dehydration, low blood sugar or reduced oxygen-carrying capacity from anaemia. A racing or irregular heartbeat, chest discomfort, breathlessness, paleness or warning dizziness adds useful detail for a clinician. The event may be harmless, but fainting while exercising is not something to self-diagnose.

Stop exercising and lie the person flat, raising the legs if there is no injury or breathing difficulty. Check breathing and responsiveness, loosen tight clothing, and keep the area safe. Do not let the person drive, climb, swim or resume training until assessed. Record what the person was doing, any symptoms before the blackout, how long recovery took, recent illness, food and fluid intake, and medicines. Avoid giving food or drink until fully alert.

Call emergency services if fainting is accompanied by chest pain, severe breathlessness, a persistent irregular heartbeat, seizure-like movements, serious injury, confusion, or failure to wake promptly. Urgent assessment is also appropriate when the episode happened at peak exertion, occurred without warning, or has happened more than once. Dehydration and Hypoglycaemia are among the possibilities clinicians may check, but an evaluation is needed to identify the cause.

Ask whether you need an ECG, blood tests, heart monitoring or specialist review, and which activities are safe while testing is underway. Mention family history of sudden cardiac problems and any palpitations, even if they stopped.